Method for wireless communication by remotely controlling beamforming

This application is a 371 National Stage of International Application No. PCT/JP2021/002852, filed on Jan. 27, 2021. The entire disclosure of the above application is incorporated herein by reference.

The present invention relates to a wireless communication method and a wireless communication device.

Toward the spread of the 5th generation mobile communication system (the following, referred as “5G”) and the local 5G, base stations are being installed in a wireless communication service providing area. The base station used for 5G and local 5G includes a centralized unit (CU), a distributed unit (DU), and a radio unit (RU) (refer to NPL 1). In addition, a plurality of combinations is defined as combinations of the centralized unit, the distributed unit, and the radio unit (refer to NPL 2).

[NPL 1] Anil Umesh, and three others, “O-RAN Front Haul Specification Outline,” NTT DOCOMO Technical Journal Vol. 27, No. 1 (April 2019) [NPL 2] NGMN (Next Generations Mobile Networks) Alliance, “NGMN Overview on 5G PAN Functional Decomposition,”2018.

16 FIG. 200 200 is a diagram showing a configuration example of a conventional wireless communication system of 5G and local 5G. A wireless communication system includes a host device, a centralized unit, a distributed unit, and one or more radio units. Transmission using a digital RoF (Radio-over-Fiber) such as eCPRI is performed between the distributed unit and one or more radio units.

16 FIG. 200 1 200 3 200 1 200 3 201 1 200 3 In, the radio unit-to-, are existing radio units in provision area of a wireless communication service. Each of the radio units-to-executes radio communication with a wireless terminal (not shown) in the cover area-to-(cell).

200 200 In a conventional wireless communication system, since transmission using digital RoF is performed between a distributed unit and a radio unit, when converting a radio signal into an optical digital signal, a band of an optical signal larger than a band of the radio signal is required, and transmission efficiency is reduced. Further, the conventional radio unitincludes an O/E (Optical to Electrical) conversion unit, an E/O (Electrical to Optical) conversion unit, a signal processing unit, a D/A (Digital to Analog) conversion unit, an A/D (Analog to Digital) conversion, and an antenna element. Therefore, it is expensive and power consumption is large. For this reason, conventionally, at some time it is impossible to suppress an increase in the facility cost for expanding the provision area of the wireless communication service.

In view of the above circumstances, the present invention aims to provide a wireless communication method and a wireless communication device capable of performing efficient optical transmission while suppressing an increase in facility cost for expanding a provision area of a wireless communication service.

among a signal processing function and a communication function provided by a wireless communication device, a centralized unit having the signal processing function transmits an optical signal having a form corresponding to the downstream radio signal to be transmitted by the communication function, to a communication target radio unit which communicates with an external communication device, among two or more radio units having the communication function connected with the centralized unit via optical fiber, and performs beamforming control of the communication target radio unit; and the communication target radio unit communicates with the external communication device according to the control of the centralized unit. An embodiment of the present invention is a wireless communication method in which

among a signal processing function and a communication function provided by a wireless communication device, a centralized unit having the signal processing function and two or more radio units having the communication function connected with the centralized unit via optical fiber; and wherein, the centralized unit transmits an optical signal having a form corresponding to the downstream radio signal to be transmitted by the communication function, to a communication target radio unit which communicates with an external communication device, among two or more radio units having the communication function connected with the centralized unit via optical fiber, and performs beamforming control of the communication target radio unit; and the communication target radio unit communicates with the external communication device according to the control of the centralized unit. An embodiment of the present invention is a wireless communication device includes

According to the present invention, efficient optical transmission can be performed while suppressing an increase in facility cost for expanding a provision area of a wireless communication service.

An embodiment of the present invention will be described in detail with reference to the diagrams.

(Overview)

1 FIG. 1 1 2 3 3 4 5 1 5 5 1 5 5 5 2 3 3 2 m m is a diagram showing a configuration example of a wireless communication systemaccording to each embodiment. The wireless communication systemincludes a host deviceand a base station. The base stationincludes a centralized unitand a plurality of radio units-to-. Here, m is an integer of 2 or more. Note that, in the following description, if it is not particularly distinguished, the radio unit-to-will be described as the radio unit. The radio unitsare arranged in multiple planes in a provision area of wireless communication service. In the following description, the direction from the host deviceto the base stationis defined as the downward direction, and the direction from the base stationto the host deviceis defined as the upward direction.

2 4 6 4 5 1 5 7 7 4 5 1 5 4 5 1 7 1 4 5 7 m m m m. 1 FIG. The host deviceand the centralized unitare connected through a coaxial cable(communication line). The centralized unitand each radio unit-to-are connected through an optical fiber. The optical fibermay be one or more single core fibers or a multi-core fiber having one or more cores. In, the centralized unitand each radio unit-to-are connected by point-to-point (P-P) For example, the centralized unitand the radio unit-are connected through an optical fiber-, and the centralized unitand the radio unit-are connected through an optical fiber-

4 5 1 5 4 5 1 5 4 5 1 5 4 5 1 5 4 5 1 5 m m m m m The centralized unitand each radio unit-to-may be connected by a passive optical network (PON). When the centralized unitand each radio unit-to-are connected through a PON, an optical splitter (branching unit) is provided between the centralized unitand each radio unit-to-. The optical splitter branches the optical signal input from the centralized unitand outputs the signal to each radio unit-to-. The passive optical network is, for example, a WDM-PON (Wavelength Division Multiplexing-Passive Optical Network), or a TDM-PON (Time Division Multiplexing-Passive Optical. Network). In the following description, it is assumed that the centralized unitand each radio unit-to-are connected by point-to-point.

2 4 The host deviceoutputs the downstream data to the centralized unit.

4 5 4 5 8 5 4 5 1 5 4 5 4 3 i m The centralized unitgenerates downstream optical signals for each radio unitby performing predetermined signal processing (for example, packetization and encoding) on the downstream data. For example, the centralized unitgenerates a downstream optical signal destined to radio unitthat is a target for communication with one or more wireless terminals-(hereinafter, referred to as “communication target radio unit”). Note that i is an integer of 1 or more. I is an integer of 1 or more. Analog RoF transmission is used between the centralized unitand each radio unit-to-. In the analog RoF, an optical signal intensity-modulated according to a radio signal is transmitted through an optical fiber. The centralized unitoutputs the generated downstream signal to the radio unit. The centralized unithas a signal processing function of separating a signal processing function and a communication function provided by the base station.

5 3 5 5 5 8 5 4 8 5 5 4 4 8 5 5 5 i i i The radio unithas a communication function, of which a signal processing function and a communication function provided by the base stationare separated. Therefore, the radio unitincludes at least a plurality of antenna elements and one or more optic/electric conversion units. The radio unitmay include an amplifier for amplifying signal intensity. In addition, the radio unitperform wireless communication with wireless terminal-. For example, the radio unitforms a beam by being remotely controlled by the centralized unitand performs wireless communication with a wireless terminal-. Furthermore, a communication target radio unitamong the radio unitsis selected by a centralized unit. For example, when communication is performed between the centralized unitand the wireless terminal-via the radio unit, the radio unithaving the best communication quality is selected as the communication target radio unit.

5 7 5 8 8 i i A communication target radio unitextracts a downstream radio signal from the optical signal by using optic electric (Optical-to-Electrical) conversion to the downstream optical signal subjected to analog RoF transmission through the optical fiber. One or more antenna elements included in the communication target radio unittransmit a downstream radio signal to a wireless terminal-. The wireless terminal-separates a stream corresponding to a downstream radio signal by signal processing such as MIMO (Multiple Input Multiple Output) signal processing.

5 8 i. The following four modes are assumed as the communication mode between the radio unitand the wireless terminal-

(First Communication Mode)

5 5 1 8 8 1 i A single radio unit(for example, the radio unit-), and a single wireless terminal-(for example, a wireless terminal-) communicate with each other.(Second Communication Mode) 5 1 5 5 1 5 2 8 8 1 m i A plurality of radio units-to-(for example, radio units-to-) and a single wireless terminal-(for example, wireless terminal-) communicate with each other.(Third Communication Mode) 5 5 1 8 8 1 8 2 i A single radio unit(for example, the radio unit-) and a plurality of wireless terminals-(for example, the wireless terminals-to-) communicate with each other.(Fourth Communication Mode) 5 1 5 5 1 5 2 8 8 1 8 2 m i A plurality of radio units-to-(for example, the radio units-to-) and a plurality of wireless terminals-(for example, the wireless terminals-to-) communicate with each other.

1 In the following description, a plurality of operations will be described with reference to a plurality of embodiments on the assumption that the wireless communication systemperforms communication in the first communication mode. The second and subsequent communication modes will be described with reference to the configuration described in the first communication mode.

2 FIG. 1 FIG. 1 FIG. 3 3 4 5 1 5 4 4 5 1 5 5 1 5 5 1 5 5 1 a a a a a m a a a m m a a m a is a diagram showing a configuration of a base stationaccording to the first embodiment. The base stationis provided with a centralized unitand a plurality of radio units-to-. The centralized unitcorresponds to the centralized unitshown in. The radio unit-to-correspond to the radio unit-to-in. Since the radio unit-to-have the same configuration, the radio unit-is explained as an example.

4 41 42 43 a The centralized unitincludes a radio unit selection unit, a signal processing unit, and a first electric/optic conversion unit.

41 5 41 5 5 41 5 5 5 The radio unit selection unitselects a communication target radio unit. The radio unit selection unitselects a communication target radio unitby using a signal from a wireless terminal received via each radio unit. For example, the radio unit selection unitmay determine the radio unithaving the best communication quality by SNR (Signal to Noise Ratio) or the like without demodulating a signal from a wireless terminal received via each radio unit, or may determine the radio unithaving the best communication quality by BER (Bit Error Rate) or the like after demodulating.

42 2 42 5 5 5 42 43 The signal processing unitperforms signal processing on the downstream data (radio signal) output from the host device. The signal processing unitin the first embodiment further performs signal processing on the control signal. The control signal in the first embodiment is a signal for performing control related to beam forming of the radio unit, and includes, for example, information indicating which of a plurality of antenna elements included in the radio unitis used for communication, information related to a phase of the antenna element included in the radio unit, and the like. The signal processing unitoutputs the radio signal and the control signal after the signal processing to the first electric/optic conversion unit.

43 42 43 The first electric/optic conversion unitconverts the radio signal and the control signal output from the signal processing unitinto optical signals of different wavelengths. The first electric/optic conversion unitoutputs the converted optical signal by WDM.

5 1 51 1 52 1 1 52 1 53 1 54 1 a o The radio unit-includes a demultiplexer-, a plurality of first optic/electric conversion units--to--(o is an integer of 1 or more), an array antenna control unit-, and antenna unit-.

51 1 7 1 51 1 52 1 1 52 1 51 1 52 1 1 51 1 52 o o The demultiplexer-demultiplexes the optical signal input through the optical fiber-. For example, the demultiplexer-demultiplexes the wavelength division multiplexed optical signal into a plurality of optical signals having different wavelengths. Second optic/electric conversion units--to--are connected to a plurality of output ports of the demultiplexer-. For example, the second optic/electric conversion unit-is connected to an output port for outputting an optical signal of a wavelength λin the demultiplexer-, and the second optic/electric conversion unit-is connected to an output port for outputting an optical signal, of a wavelength λo.

52 1 1 52 1 51 1 52 1 1 52 1 52 1 52 1 51 1 52 1 7 1 o o The second optic/electric conversion units--to--convert optical signals input thorough the demultiplexer-into electrical signals. It should be noted that the number of the second optic/electric conversion unit--to--may be one. When there is one second optic/electric conversion unit-, the second optic/electric conversion unit-is provided in the front stage of the demultiplexer-. The second optic/electric conversion units-converts an optical signal transmitted via the optical fiber-into an electrical signal.

53 1 54 1 The array antenna control unit-performs beam control of the array antenna unit-on the basis of the input control signal.

54 1 55 1 1 55 1 55 1 1 55 1 54 1 52 1 1 55 1 1 55 1 53 1 n n n The array antenna unit-has a plurality of antenna elements--to--. The antenna elements--to--are provided on the array. The array antenna unit-emits an electric signal corresponding to the radio signal output from the second optic/electric conversion unit--via the antenna elements--to--in accordance with the control of the array antenna control unit-.

3 a An operation example of the base stationwill be described below.

3 FIG. 3 FIG. 3 5 1 5 a a a. is a diagram showing an operation of a base stationaccording to the first embodiment. In, it is assumed that the radio unit-is the communication target radio unit

42 101 42 43 The signal processing unitperforms signal processing on the radio signal and the control signal (step S). The signal processing unitoutputs the radio signal and the control signal after the signal processing to the first electric/optic conversion unit.

43 42 102 43 103 43 5 5 1 7 43 7 1 104 5 1 7 1 a a a The first electric/optic conversion unitconverts the radio signal and the control signal output from the signal processing unitinto optical signals of different wavelengths, respectively (step S). The first electric/optic conversion unitperforms wavelength division multiplexing of the converted optical signal (step S). The first electric/optic conversion unittransmits the wavelength division multiplexed optical signal to a communication target radio unit(radio unit-) via an optical fiber. For example, the first electric/optic conversion unittransmits the wavelength division multiplexed optical signal through an optical fiber-(step S). The wavelength division multiplexed optical signal is transmitted to a radio unit-via the optical fiber-.

5 1 7 1 51 1 105 52 1 1 52 1 a o. The radio unit-receives the optical signal transmitted through the optical fiber-. The demultiplexer-demultiplexes the received optical signal (step S). As a result, the optical signal of the wavelength λ1 is input to the first optic/electric conversion unit--, and the optical signal of the wavelength λo is input to the first optic/electric conversion unit--

52 1 1 1 106 52 1 1 54 1 The first optic/electric conversion unit--converts the input optical signal of the wavelength λinto an electric signal (step S). The electric signal is an electric signal corresponding to a radio signal. The first optic/electric conversion unit--outputs the electric signal to the array antenna unit-.

52 1 106 52 1 53 1 o o The second optic/electric conversion unit--converts the input optical signal of the wavelength λo into an electric signal (step S). The electric signal is an electric signal corresponding to a control signal. The first optic/electric conversion unit--outputs the electric signal to the array antenna control unit-.

53 1 54 1 107 53 1 55 1 1 55 1 54 1 54 1 54 1 53 1 108 n The array antenna control unit-performs beam control of the array antenna unit-on the basis of the input electric signal (step S). The array antenna control unit-controls a plurality of antenna elements--to--provided by the array antenna unit-to emit radio signals in response to electrical signals input to the array antenna unit-. The array antenna unit-radiates a radio signal corresponding to the input electric signal in accordance with the control of the array antenna control unit-(step S). In this way, the optical signal is transmitted using the analog RoF.

3 3 4 5 5 4 4 5 5 4 3 4 5 5 a a a a a a a a a a a a a a According to the base stationconfigured as described above, in a configuration in which the function of the base stationis divided into the centralized unitand the radio unit, a plurality of radio unitsare connected to the centralized unit, and the centralized unitremotely controls beam forming of one or more radio units. Thus, each radio unitcan only form a beam according to an instruction from the centralized unit. Further, the base stationin the first embodiment performs analog RoF transmission between the centralized unitand the radio unit. Thus, it is not necessary to provide a digital-to-analog conversion unit for processing a digital signal in the radio unitand an analog-to-digital conversion unit, and an increase in the band of the optical signal can be suppressed, so that efficient optical transmission can be performed.

Thus, efficient optical transmission can be performed while suppressing an increase in facility cost for expanding a provision area of the wireless communication service.

A conventional radio unit (RU) includes a digital-to-analog conversion unit and an analog-to-digital conversion unit. Conventionally, when a wireless communication service providing area is expanded, a large number of radio units must be installed in the wireless communication service providing area in accordance with frequency characteristics such as linearity and attenuation of millimeter waves. In addition, in a wireless communication service providing area, it is sometimes difficult to install a radio unit at a high place such as a wall surface, a traffic light, a street lamp, or the like. Furthermore, the power consumption of the radio unit may be high. For these reasons, there are problems such as an increase in cost of equipment investment.

5 5 5 5 a a a a On the other hand, in the first embodiment, since the radio unitdoes not include the digital-to-analog conversion unit and the analog-to-digital conversion unit, it is possible to suppress an increase in the cost of the facility investment compared with the conventional radio unit. Furthermore, since the radio unitdoes not include a digital-to-analog conversion unit and an analog-to-digital conversion unit, it is smaller and lighter than a conventional radio unit. Therefore, the radio unitcan be easily installed even in a place (where installation load is large) such as a high place, a wall surface, a traffic light and a street lamp. That is, the radio unitcan improve flexibility of an installation place.

In the second embodiment, the difference from the first embodiment is that the centralized unit performs subcarrier multiplexing (SCM). In the second embodiment, differences with the first embodiment will be mainly described. In the second embodiment, the centralized unit multiplexes electric signals of different frequency components to one optical wavelength by subcarrier multiplexing and transmits the multiplexed electric signals to the radio unit.

4 FIG. 1 FIG. 1 FIG. 3 3 4 5 1 5 4 4 5 1 5 5 1 5 5 1 5 5 1 b b b b b m b b b m m b b m b is a diagram showing a configuration of a base stationaccording to the second embodiment. The base stationis provided with a centralized unitand a plurality of radio units-to-. The centralized unitcorresponds to the centralized unitshown in. The radio units-to-correspond to the radio units-to-in. Since the radio units-to-have the same configuration, the radio unit-will be described as an example.

4 41 42 43 b b. The centralized unitincludes a radio unit selection unit, a signal processing unit, and a first electric/optic conversion unit

43 42 43 b b The first electric/optic conversion unitsubcarrier-multiplexes the radio signal and the control signal output from the signal processing unitwith the same wavelength and converts them into an optical signal. It is assumed that the radio signal and the control signal inputted to the first electric/optic conversion unithave different frequency components in an electric domain. For example, it is assumed that the frequency of the radio signal is defined as f1, and the frequency of the control signal is defined as f2. It is assumed that f1 is not equal to f2, and the radio signal and the control signal do not overlap in the frequency region.

5 1 51 1 52 1 53 1 54 1 5 1 5 1 5 1 52 1 52 1 7 1 51 1 b b b b a b b b b The radio unit-is provided with a demultiplexer-, a first optic/electric conversion unit-, an array antenna control unit-, and an array antenna unit-. The radio unit-is different in configuration from the radio unit-in the first embodiment in that the radio unit-includes one first optic/electric conversion unit-, and the first optic/electric conversion unit-is provided on the front stage (optical fiber-side) of the demultiplexer-.

51 1 52 1 51 1 53 1 54 1 51 1 51 1 54 1 53 1 51 1 b b b b b b A demultiplexer-demultiplexes the input electric signal. An electric signal outputted from the first optic/electric conversion unit-(for example, an electric signal subjected to subcarrier multiplexing) is input to the demultiplexer-. In the second embodiment, an array antenna control unit-and an array antenna unit-are connected to a plurality of output ports of the demultiplexer-. For example, the demultiplexer-outputs an electric signal of a frequency f1 from an output port to which the array antenna unit-is connected, and outputs an electric signal of a frequency f2 from an output port to which the array antenna control unit-is connected. In this way, the demultiplexer-separates the radio signal from the control signal by demultiplexing the input electric signal at the electric stage.

3 5 1 5 b b b. An operation example of the base stationwill be described below. Here, it is assumed that the radio unit-is a communication target radio unit

43 42 b fc−f2: A lower sideband component of an array antenna main signal fc−f1: A lower side band component of an array antenna control signal fc: Optical carrier fc+f1: An upper side band component of an array antenna control signal fc+f2: An upper side band component of an array antenna main signal The first electric/optic conversion unitsubcarrier-multiplexes the radio signal of the frequency f1 and the control signal of the frequency f2 outputted from the signal processing unitat the same wavelength and converts them into an optical signal. Thus, the spectrum of the optical domain after the subcarrier multiplexing is expressed as follows when the subcarrier multiplexing is performed on the optical wavelength fc.

43 5 5 1 7 43 7 1 5 1 7 1 b b b b b The first electric/optic conversion unittransmits the optical signal after subcarrier multiplexing to the communication target radio unit(radio unit-) via an optical fiber. For example, the first electric/optic conversion unittransmits the optical signal after subcarrier multiplexing through an optical fiber-. The optical signal after subcarrier multiplexing is transmitted to the radio unit-via the optical fiber-.

5 1 7 1 52 1 52 1 51 1 51 1 52 1 b b b b b b The radio unit-receives a signal transmitted via the optical fiber-. The first optic/electric conversion unit-converts a received optical signal into an electrical signal. The first optic/electric conversion unit-outputs the electric signal to the demultiplexer-. The demultiplexer-demultiplexes the electric signal output from the second optic/electric conversion unit-. As described above, since the radio signal and the control signal do not overlap each other in the frequency domain, the radio signal and the control signal can be demultiplexed.

51 1 53 1 54 1 53 1 54 1 b The electric signal demultiplexed by the demultiplexer-is input to the array antenna control unit-and the array antenna unit-. The array antenna control unit-performs the beam control of the array antenna unit-on the basis of the input electric signal.

53 1 55 1 1 55 1 54 1 54 1 54 1 53 1 n The array antenna control unit-controls a plurality of antenna elements--to--provided in the array antenna unit-, and emits radio signals corresponding to electrical signals input to the array antenna unit-. The array antenna unit-radiates a radio signal corresponding to the input electric signal in accordance with the control of the array antenna control unit-. In this way, the optical signal is transmitted using the analog RoF.

3 b By the base stationthat has the foregoing configuration, it is possible to obtain similar advantages to the advantages of the first embodiment.

3 52 5 5 5 b b b a b Further, in the base station, the number of second optic/electric conversion unitsprovided in the radio unitis smaller than that of the radio unitin the first embodiment. Accordingly, the fabricating cost of the radio unitalso can be reduced.

In the third embodiment, the difference from the first embodiment is that the phase adjustment of the optical signal is performed in the centralized unit. In the third embodiment the differences from the first embodiment will be described mainly.

5 FIG. 1 FIG. 1 FIG. 3 3 4 5 1 5 4 4 5 1 5 5 1 5 5 1 5 5 1 c c c c c m c c c m m c c m c is a diagram showing a configuration of a base stationaccording to the third embodiment. The base stationis provided with a centralized unitand a plurality of radio units-to-. The centralized unitcorresponds to the centralized unitshown in. The radio units-to-corresponds to the radio units-to-shown in. Since the radio units-to-have the same configuration, the radio unit-will be described as an example.

4 41 42 43 1 43 44 1 44 45 42 2 42 43 1 43 c c c c n n c c c c n. The centralized unitincludes a radio unit selection unit, a signal processing unit, a plurality of first electric/optic conversion units-to-, a plurality of phase adjustment units-to-, and a multiplexer. The signal processing unitperforms signal processing to the downstream data output from the host device. The signal processing unitoutputs the radio signal to the first electric/optic conversion units-to-

43 1 43 42 43 1 43 c c n c c n The first electric/optic conversion units-to-converts a radio signal output from the signal processing unitinto n optical signals of different wavelength. For example, the first electric/optic conversion units-converts the radio signal into an optical signal having a wavelength λ1. For example, the first optic/electric conversion unit-converts the radio signal into an optical signal of a wavelength λn.

44 1 44 43 3 43 44 1 44 44 1 44 n c c n n n The phase adjustment units-to-adjust the phase of the optical signal converted by the first optic/electric conversion unit-to-. More specifically, the phase adjustment units-to-adjust the phase so as to match the phase of the optical signal input to the phase adjustment units-to-. As a method of adjusting the phase of the optical domain, a method of adjusting the optical path length by using an optical delay device or the like, or a method of adjusting the phase by adjusting the refractive index by using a dispersion control device or the like may be used. The phase adjustment may be performed by an analog signal or a digital signal.

45 44 1 44 45 45 n A multiplexermultiplexes the optical signals phase-adjusted by the phase adjustment units-to-. Thus, the multiplexergenerates a wavelength division multiplexed optical signal. The multiplexeroutputs the wavelength-multiplexed optical signal.

5 1 51 1 52 1 1 52 1 55 1 1 55 1 55 1 1 55 1 52 1 1 52 1 55 1 1 52 1 1 c n n n n The radio unit-has a demultiplexer-, a plurality of first optic/electric conversion units--to--, and a plurality of antenna elements--to--. One of antenna elements--to--is connected to each of the first optic/electric conversion units--to--. For example, the antenna element--is connected to the first optic/electric conversion unit--.

3 c An operation example of the base stationwill be described below.

6 FIG. 6 FIG. 3 5 1 5 c c c. is a diagram showing an operation example of the base stationaccording to the third embodiment. In, it is assumed that the radio unit-is a communication target radio unit

42 201 42 43 1 43 42 43 1 43 42 43 1 43 42 202 43 1 43 44 1 44 c c c c n c c c n c c c n c c c n n. The signal processing unitperforms signal processing to the radio signal (step S). The signal processing unitoutputs the radio signal after the signal processing to the first electric/optic conversion units-to-. The radio signal output from the signal processing unitis demultiplexed into n pieces and input to the first electric/optic conversion units-to-. The demultiplexing of the radio signal may be performed, for example, by using a demultiplexer of one input and multiple output, or by physically connecting a plurality of lines to the output side of the signal processing unit. The first electric/optic conversion units-to-converts the radio signal output from the signal processing unitinto n optical signals of different wavelengths (step S). The first electric/optic conversion units-to-output optical signals after conversion to the phase adjustment units-to-

44 1 44 203 44 1 44 45 45 44 1 44 204 45 5 5 1 7 45 7 1 205 5 1 7 1 n n n c c c The phase adjustment units-to-adjust the phase of the input optical signal (step S). The phase adjustment units-to-output the optical signal after the phase adjustment to the multiplexer. The multiplexerperforms wavelength division multiplexing of the optical signal whose phase is adjusted by the phase adjustment units-to-(step S). The multiplexertransmits the wavelength division multiplexed optical signal to a communication target radio unit(radio unit-) via an optical fiber. For example, the multiplexertransmits the wavelength-division multiplexed optical signal through the optical fiber-(step S). The wavelength division multiplexed optical signal is transmitted to a radio unit-via an optical fiber-.

105 106 7 1 51 1 52 1 1 52 1 52 1 3 52 1 55 1 1 55 1 55 1 1 55 1 204 n n n n Thereafter, in the processing of steps Sand S, the optical signal transmitted through the optical fiber-is demultiplexed by a demultiplexer-, and the demultiplexed optical signal is converted into an electric signal by the first optic/electric conversion units--to--. The electric signal converted by the first optic/electric conversion units--to--are input to the antenna elements--to--. The antenna elements--to--radiate the radio signal corresponding to the electrical signal (step S). In this way, the optical signal is transmitted using the analog RoF.

3 c By the base stationthat has the foregoing configuration, it is possible to obtain similar advantages to the advantages of the first embodiment.

3 52 1 1 52 1 51 1 55 1 1 55 1 52 1 1 52 1 5 4 c n n n c d. Further, in the base station, the second optic/electric conversion units--to--are connected to the output side of demultiplexer-, and the antenna elements--to--are connected to the output side of the second optic/electric conversion units--to--. Thus, the beam formed by the radio unitcan be controlled by phase adjustment in the centralized unit

4 43 1 43 4 43 1 3 3 4 5 1 5 4 4 5 1 5 5 1 5 54 1 5 5 1 5 c c c n c c d d d d d m d d d m m d m c d m 7 FIG. 1 FIG. 1 FIG. 5 FIG. In the above configuration, the centralized unitis provided with n first electric/optic conversion units-to-, but the centralized unitmay be provided with one first electric/optic conversion unit-.is a diagram showing a configuration of a base stationaccording to the variant example of the third embodiment. The base stationis provided with a centralized unitand a plurality of radio units-to-. The centralized unitcorresponds to the centralized unitshown in. The radio units-to-corresponds to the radio units-to-shown in. Since the function unit provided in the radio units-to-has the same configuration as the radio units-to-in, description thereof will be omitted.

4 41 42 43 44 1 44 45 46 4 43 46 43 44 1 44 d d d n d d d n. The centralized unitincludes a radio unit selection unit, a signal processing unit, a first electric/optic conversion unit, a plurality of phase adjustment units-to-, a multiplexerand a demultiplexer. The centralized unitis provided with one first electric/optic conversion unit, and the demultiplexeris provided between the first electric/optic conversion unitand the plurality of phase adjustment units-to-

43 42 43 43 46 d d d d The first electric/optic conversion unitconverts the radio signal output from the signal processing unitinto n optical signals of different wavelengths. For example, the first electric/optic conversion unitconverts the radio signal into an optical signal having wavelengths λ1 to λo. The first electric/optic conversion unitoutputs the converted n optical signals to a demultiplexer.

46 43 46 44 1 44 44 1 44 d n n A demultiplexerdemultiplexes the n optical signals output from the first electric/optic conversion unit. The optical signal demultiplexed by the demultiplexeris input to the phase adjustment units-to-. For example, an optical signal of a wavelength λ1 is input to the phase adjustment unit-, and an optical signal of a wavelength λn is input to the phase adjustment unit-. Thereafter, the flow is the same as that described in the third embodiment.

In the fourth embodiment, the difference from the first embodiment is that the phase adjustment of the electric signal is performed in the centralized unit. In the fourth embodiment, differences from the first embodiment will be described mainly.

8 FIG. 1 FIG. 1 FIG. 3 3 4 5 1 5 4 4 5 1 5 5 1 5 5 1 5 5 1 e e e e e m e e e m m e e m e is a diagram showing a configuration example of a base stationaccording to the fourth embodiment. The base stationis provided with a centralized unitand a plurality of radio units-to-. The centralized unitcorresponds to the centralized unitshown in. The radio units-to-respectively, correspond to the radio units-to-shown in. Since the radio units-to-have the same configuration, the description will be made with the radio unit-as an example.

4 41 42 43 1 43 44 1 44 45 42 44 43 e e e e n n e, n e The centralized unitincludes a radio unit selection unit, a signal processing unit, a plurality of first electric/optic conversion units-to-, a plurality of phase adjustment units-to-, and a multiplexer. On the output side of the signal processing unitcombinations (systems) of the phase adjustment unitand the first electric/optic conversion unitare provided.

42 2 42 44 1 44 e e n. A signal processing unitperforms signal processing on the downstream data output from the host device. The signal processing unitoutputs radio signals to the phase adjustment units-to-

44 1 44 42 44 1 44 44 1 44 n n n The phase adjustment units-to-adjusts the phase of the radio signal output from the signal processing unit. More specifically, the phase adjustment units-to-adjusts the phase so as to match the phase of the radio signal input to the phase adjustment units-to-. As a method of adjusting the phase of the electric domain, a method of adjusting the path length by using a delay device or the like, a method of adjusting the phase of a radio signal by using a phase shifter or the like may be used. The phase adjustment may be performed by an analog signal or a digital signal.

43 1 43 43 1 43 e e n e e n The first electric/optic conversion units-to-converts the phase adjusted radio signal into n optical signals of different wavelengths. For example, the first electric/optic conversion units-converts the phase adjusted radio signal into an optical signal having the wavelength λ1. For example, the first electric/optic conversion unit-converts the phase adjusted radio signal into an optical signal having a wavelength λo.

45 43 1 43 45 45 e e n The multiplexermultiplexes the optical signals converted by the first electric/optic conversion units-to-. Thus, the multiplexergenerates a wavelength division multiplexed optical signal. The multiplexeroutputs the wavelength-multiplexed optical signal.

3 5 1 5 e e e. An operation example of the base stationwill be described below. Here, it is assumed that the radio unit-is a communication target radio unit

42 42 44 1 44 42 44 1 44 44 1 44 44 1 44 43 1 43 e e n e n n n e e n. The signal processing unitperforms signal processing on the radio signal. The signal processing unitoutputs the radio signal after the signal processing to a phase adjustment units-to-. The radio signal output from the signal processing unitis demultiplexed into n pieces and input to the phase adjustment units-to-. The phase adjustment units-to-adjust the phase of the input radio signal. The phase adjustment units-to-output the radio signal after the phase adjustment to the first electric/optic conversion units-to-

43 1 43 44 1 44 43 1 43 45 45 45 45 43 1 43 45 5 5 1 7 45 7 1 5 1 7 1 e e n n e e n e e n e e e The first electric/optic conversion units-to-converts the radio signal output from the phase adjustment units-to-into n optical signals of different wavelengths. The first electric/optic conversion units-to-output the converted optical signal to the multiplexer. The multiplexeroutputs the converted optical signal to the multiplexer. The multiplexerwavelength-divides and multiplexes the optical signal converted by the first electric/optic conversion units-to-. The multiplexertransmits the wavelength division multiplexed optical signal to the communication target radio unit(radio unit-) via an optical fiber. For example, the multiplexertransmits the wavelength division multiplexed optical signal through the optical fiber-. The wavelength division multiplexed optical signal is transmitted to a radio unit-via an optical fiber-.

105 106 7 1 51 1 52 1 1 52 1 52 1 1 52 1 55 1 1 55 1 55 1 1 55 1 n n n n Thereafter, in the processing of steps Sand S, the optical signal transmitted through the optical fiber-is demultiplexed by a demultiplexer-, and the demultiplexed optical signal is converted into an electric signal by the first optic/electric conversion units--to--. The electric signals converted by the first optic/electric conversion units--to--are input to the antenna elements--to--. The antenna elements--to--radiate radio signals corresponding to the input signals. In this way, the optical signal is transmitted using the analog RoF.

3 e By the base stationthat has the foregoing configuration, it is possible to obtain similar advantages to the advantages of the first embodiment.

3 52 1 1 52 1 51 1 55 1 1 55 1 52 1 1 52 1 5 4 e n n n e e. Further, in the base station, the first optic/electric conversion units--to--are connected to output side of the demultiplexer-, and the antenna elements--to--are connected to output side of the second optic/electric conversion units--to--. Thus, the beam formed by the radio unitcan be controlled by phase adjustment in the centralized unit

In the fifth embodiment, the difference from the first embodiment is that a beam forming circuit is used for forming a beam in the radio unit. In the fifth embodiment, differences from the first embodiment will be described mainly.

9 FIG. 1 FIG. 1 FIG. 3 3 4 5 1 5 4 4 5 1 5 5 1 5 5 1 5 5 1 f f f f f m f f f m m f f m f is a diagram showing a configuration example of a base stationaccording to the fifth embodiment. The base stationis provided with a centralized unitand a plurality of radio units-to-. The centralized unitcorresponds to the centralized unitshown in. The radio unit-to-corresponds to the radio unit-to-shown in. Since the radio unit-to-have the same configuration, the description will be made with the radio unit-as an example.

4 41 42 43 47 f f f The centralized unitincludes a radio unit selection unit, a signal processing unit, a first electric/optic conversion unit, and a wavelength control unit.

42 2 42 43 47 f f f The signal processing unitperforms signal processing on the downstream data output from the host device. The signal processing unitoutputs the radio signal to the first electric/optic conversion unitand outputs the control signal to the wavelength control unit.

47 43 42 47 43 f f f The wavelength control unitcontrols the wavelength of the first electric/optic conversion uniton the basis of the control signal outputted from the signal processing unit. Specifically, the wavelength control unitdesignates a wavelength when the first electric/optic conversion unitconverts the radio signal into the optical signal.

43 42 47 f f The first electric/optic conversion unitconverts the radio signal output from the signal processing unitinto an optical signal of a wavelength designated by the wavelength control unit.

5 1 51 1 52 1 1 52 1 55 1 1 55 1 56 1 5 1 5 1 5 1 56 1 53 1 54 1 f n n f a f The radio unit-includes a demultiplexer-, a plurality of first optic/electric conversion units--to--, a plurality of antenna elements--to--, and a beam forming circuit-. The configuration of the radio unit-is different from that of the radio unit-in the first embodiment in that the radio unit-is provided with a beam forming circuit-instead of the array antenna control unit-and the array antenna unit-.

56 1 52 1 1 52 1 56 1 55 1 1 55 1 56 1 56 1 56 1 56 1 n n The beam forming circuit-has a plurality of input ports and a plurality of output ports. The first optic/electric conversion units--to--are connected to the input ports of the beam forming circuit-. The antenna elements--to--are connected to the output ports of the beam forming circuit-. When a signal is input to one input port of the beam forming circuit-, a signal having the same amplitude and a linearly inclined phase is output from the output port. The beam forming circuit-has different phase slopes for different input ports. The beam forming circuit-can form a beam in a direction corresponding to the input port. The beam forming circuit is one aspect of an antenna unit.

56 1 56 1 (reference document 1: Luo, Q., Gao, S. S., Liu, W., & Gu, C., “Low-cost Smart Antennas”, Wiley, p. 253-265) The beam forming circuit-has the reversibility of input-output, and when a signal arrives from the direction of the beam corresponding to a certain input port, the signal is outputted only from the input port. The beam forming circuit-includes, for example, a butler matrix, a brass matrix, a no-run matrix, a Rotman lens, etc., (for example, refer to reference document 1).

3 f An operation example of the base stationwill be described below.

10 FIG. 10 FIG. 3 5 1 5 f f f. is a diagram showing an operation example of the base stationaccording to the fifth embodiment. In, it is assumed that the radio unit-is the communication target radio unit

42 101 42 43 47 f f f The signal processing unitperforms signal processing on the radio signal and the control signal (step S). The signal processing unitoutputs the radio signal after signal processing to the first optic/electric conversion unit, and outputs the control signal after signal processing to the wavelength control unit.

47 43 301 47 43 43 42 47 302 43 42 47 f f f f f f The wavelength control unitcontrols the wavelength of the first electric/optic conversion uniton the basis of the control signal (step S). For example, the wavelength control unitdesignates a wavelength when the first electric/optic conversion unitconverts the radio signal into the optical signal on the basis of information on the wavelength included in the control signal. For example, it is assumed that the wavelength information included in the control signal is a wavelength λ1. The first electric/optic conversion unitconverts the radio signal output from the signal processing unitinto an optical signal of a wavelength designated by a wavelength control unit(step S). For example, the first electric/optic conversion unitconverts the radio signal output from the signal processing unitinto an optical signal of a wavelength λ1 designated by the wavelength control unit.

43 5 5 1 7 43 7 1 303 5 1 7 1 f f f f f The first electric/optic conversion unittransmits an optical signal of a wavelength λ1 to a communication target radio unit(radio unit-) via an optical fiber. For example, the first electric/optic conversion unittransmits an optical signal of a wavelength λ1 by an optical fiber-(step S). The optical signal of the wavelength λ1 is transmitted to the radio unit-via the optical fiber-.

5 1 7 1 51 1 304 5 1 51 1 51 1 52 1 1 f f The radio unit-receives the optical signal transmitted through the optical fiber-. The demultiplexer-demultiplexes the received optical signal (step S). The optical signal received by the radio unit-is an optical signal of a wavelength λ1. Therefore, the optical signal output from the demultiplexer-is an optical signal having a wavelength λ1. The optical signal output from the demultiplexer-is input to the first optic/electric conversion unit--.

52 1 1 305 52 1 1 56 1 The first optic/electric conversion unit--converts the input optical signal having a wavelength λ1 into an electric signal (step S). The first optic/electric conversion unit--outputs the electric signal to the beam forming circuit-.

56 1 52 1 1 56 1 306 55 1 55 1 108 The beam forming circuit-inputs the electric signal output from the first optic/electric conversion unit--. The beam forming circuit-forms a beam in a direction corresponding to an input port to which an electric signal is input (step S). As a result, a radio signal is emitted from the antenna element-connected to the output port corresponding to the input port to which the electric signal is input. The antenna element-connected to an output port corresponding to an input port to which an electric signal is input radiates a radio signal corresponding to the input electric signal (step S). In this way, the optical signal is transmitted using the analog RoF.

3 f In the base stationthat has the foregoing configuration, it is possible to obtain similar advantages to the advantages of the first embodiment.

3 4 56 5 56 3 5 4 f f f f f f. Further, in the base station, the wavelength is switched by the centralized unit, so that an input port of an electric signal input to a beam forming circuitprovided in the radio unitis changed. Thus, the beam direction formed by the beam forming circuitis changed. Thus, in the base station, the direction of the beam formed by the radio unitcan be controlled by switching the wavelength by the centralized unit

In the sixth embodiment, the difference from the first embodiment is that a reflector antenna is used for forming a beam in the radio unit. In the sixth embodiment, differences from the first embodiment will be described mainly.

11 FIG. 1 FIG. 1 FIG. 3 3 4 5 1 5 4 4 5 1 5 5 1 5 5 1 5 5 1 4 4 g g f g g m f g g m m g q m g f f is a diagram showing a configuration example of a base stationaccording to the sixth embodiment. The base stationis provided with a centralized unitand a plurality of radio units-to-. The centralized unitcorresponds to the centralized unitshown in. The radio units-to-corresponds to the radio unit-to-shown in. Since the radio units-to-have the same configuration, the description will be made with the radio unit-as an example. In the sixth embodiment, the configuration of the centralized unitis the same as the centralized unitin the fifth embodiment, and thus a description thereof is omitted.

5 1 51 1 52 1 1 52 1 57 1 5 1 5 1 5 1 57 1 53 1 54 1 g n g a g The radio unit-includes a demultiplexer-, a plurality of first optic/electric conversion units--to--, and an antenna unit-. The configuration of the radio unit-is different from that of the radio unit-in the first embodiment in that the radio unit-is provided with an antenna unit-instead of the array antenna control unit-and the array antenna unit-.

57 1 57 1 58 1 1 58 1 59 1 n The antenna unit-is, for example, a reflector antenna. The antenna unit-is composed of a plurality of feeds--to--, and a reflect array-.

58 1 1 58 1 59 1 52 1 3 52 1 58 1 1 58 1 n n n The feeds--to--are provided facing the reflect array-, and input electrical signals output from the first optic/electric conversion units--to--. The feeds--to--radiates a radio signal corresponding to the input electric signal.

59 1 58 1 1 58 1 59 1 58 1 1 58 1 59 1 58 1 1 58 1 57 1 n n n (reference document 1: Luo, Q., Gao, S. S., Liu, W., & Gu, C., “Low-cost Smart Antennas”, Wiley, p. 165-198) The reflect array-reflects a radio signal radiated from the feeds--to--. More specifically, the reflection array-reflects the radio signal with a phase difference in a direction corresponding to the position of the feeds--to--. Thus, the reflect array-can form a beam in a direction corresponding to the position of the feeds--to--. For example, as the antenna unit-in the sixth embodiment, a reflect array in which elements having a controlled reflection phase are arranged and flattened may be used, (for example, refer to reference document 1).

58 59 1 58 59 1 58 58 When a radio signal is emitted from one feed, the reflection array-is linearly tilted in phase when reflected by the reflection array, and can form a beam in a certain direction. The gradient of the phase differs depending on the feed, and the beam direction differs. The reflect array-has reversibility of input-output, and when a radio signal arrives from the direction of a beam corresponding to a certain feed, the radio signal converges on the feed.

3 4 4 4 g f f f. An operation example of the base station apparatuswill be described below. The processing of the centralized unitis omitted because the processing of the centralized unithas been described in the fifth embodiment. Here, it is assumed that an optical signal of a wavelength λ1 is output in the centralized unit

5 1 7 1 51 1 5 1 51 1 51 1 52 1 1 g g The radio unit-receives a signal transmitted via the optical fiber-. The demultiplexer-demultiplexes the received optical signal. The optical signal received by the radio unit-is an optical signal having a wavelength λ1. Therefore, the optical signal output from the demultiplexer-is an optical signal having a wavelength λ1. The optical signal output from the demultiplexer-is input to the first optic/electric conversion unit--.

52 1 1 52 1 1 58 1 1 58 1 1 52 1 1 58 1 1 59 1 58 1 1 The first optic/electric conversion unit--converts an optical signal having a wavelength λ1 to an electric signal. The first optic/electric conversion unit--outputs the electric signal to the feed--. The feed--radiates a radio signal corresponding to the electric signal output from the first optic/electric conversion unit--. The radio signal radiated from the feed--is reflected by the reflect array-, and radiated in a direction corresponding to the position of the feed--. In this way, the optical signal is transmitted using the analog RoF.

3 g By the base stationthat has the foregoing configuration, it is possible to obtain similar advantages to the advantages of the first embodiment.

3 58 5 4 57 3 5 4 g g f g g f. Furthermore, in the base station, an electric signal input to the feedprovided in a radio unitis changed by switching a wavelength by the centralized unit. Thus, the beam direction formed by the antenna unitis changed. Thus, in the base station, the direction of the beam formed by the radio unitcan be controlled by switching the wavelength by the centralized unit

In the seventh embodiment, the difference from the first embodiment is that a lens antenna is used for forming a beam in the radio unit. In the seventh embodiment, differences from the first embodiment will be described mainly.

12 FIG. 1 FIG. 1 FIG. 3 3 4 5 1 5 4 4 5 1 5 5 1 5 5 1 5 5 1 4 4 h h f h h m f h h m m h h m h f f is a diagram showing a configuration example of a base stationaccording to the seventh embodiment. The base stationis provided with a centralized unitand a plurality of radio units-to-. The centralized unit.corresponds to the centralized unitshown in. The radio units-to-correspond to the radio unit-to-shown in. Since the radio units-to-have the same configuration, the radio unit-will be described as an example. In the seventh embodiment, the configuration of the centralized unitis the same as the centralized unitin the fifth embodiment, and thus a description thereof is omitted.

5 1 51 1 52 1 1 52 1 57 1 5 1 5 1 5 1 57 1 53 1 54 1 f n h h a h h The radio unit-includes a demultiplexer-, a plurality of first optic/electric conversion units--to--, and an antenna section-. The configuration of the radio unit-is different from that of the radio unit-in the first embodiment in that the radio unit-is provided with an antenna section-instead of the array antenna control unit-and the array antenna unit-.

57 1 57 1 58 1 1 58 1 60 1 h h n The antenna unit-is, for example, a lens antenna. The antenna unit-is composed of a plurality of feeds--to--, and a transmit array-.

52 1 1 52 1 58 1 1 58 1 58 1 1 58 1 n n n The electric signals output from the first optic/electric conversion unit--to--are input to the feeds--to--. The feeds--to--radiates a radio signal corresponding to the input electric signal.

60 1 58 1 1 58 1 58 1 1 58 1 60 1 58 1 1 58 1 57 1 n n n f (reference document 1: Luo, Q., Gao. S. S., Liu, W., & Gu. C., “Low-cost Smart Antennas”, Wiley, p. 165-198) The transmit array-transmits a radio signal radiated from the feed feeds--to--with a phase difference in a direction corresponding to the position of the feeds--to--. As a result, the transmit array-can form a beam in a direction corresponding to the position of the feeds--to--. For example, as the antenna section-in the seventh embodiment, a transmit array in which elements whose transmission phase is controlled are arranged and flattened may be used (for example, refer to reference document 1).

3 4 4 4 h f f f. An operation example of the base station apparatuswill be described below. The processing of the centralized unitis omitted because the processing of the centralized unithas been described in the fifth embodiment. Here, it is assumed that an optical signal of a wavelength λ1 is output in the centralized unit

5 1 7 1 51 1 5 1 51 1 51 1 52 1 1 h h The radio unit-receives a signal transmitted via the optical fiber-. The demultiplexer-demultiplexes the received optical signal. The optical signal received by the radio unit-is an optical signal having a wavelength λ1. Therefore, the optical signal output from the demultiplexer-is an optical signal having a wavelength λ1. The optical signal output from the demultiplexer-is input to the first optic/electric conversion unit--.

52 1 1 52 1 1 58 1 1 58 1 1 52 1 1 58 1 1 60 1 58 1 1 The first optic/electric conversion unit--converts the input optical signal having a wavelength λ1 to an electric signal. The first optic/electric conversion unit--outputs the electric signal to the feed--. The feed--radiates a radio signal corresponding to the electric signal output from the first optic/electric conversion unit--. The radio signal radiated from the feed--transmits the transmit array-, and is radiated in a direction corresponding to the position of the feed--. In this way, the optical signal is transmitted using the analog RoF.

3 h By the base stationthat has the foregoing configuration, it is possible to obtain similar advantages to the advantages of the first embodiment.

3 58 5 4 57 h h f h Further, in the base station, an electric signal input to the feedprovided in a radio unitis changed by switching a wavelength by a centralized unit. Thus, the beam direction formed by the antenna unitis changed.

3 5 4 h h f. Thus, in the base station, the direction of the beam formed by the radio unitcan be controlled by switching the wavelength by the centralized unit

In the eighth embodiment, the difference from the first embodiment is that each radio unit receives an upstream optical signal. In the eighth embodiment, differences from the first embodiment will be described mainly.

5 4 4 2 4 1 FIG. In the eighth embodiment, each radio unitshown intransmits an optical signal corresponding to an upstream radio signal to a centralized unitusing an analog RoF. The centralized unitgenerates upstream data by executing predetermined signal processing on an optical signal corresponding to the upstream radio signal. The host deviceacquires upstream data from the centralized unit (CU).

13 FIG. 1 FIG. 1 FIG. 3 3 4 5 1 5 4 4 5 1 5 5 1 5 5 1 5 4 5 1 5 5 1 i i i i i m i i i m m i i m i i i m i is a diagram showing a configuration example of a base stationaccording to the eighth embodiment. The base stationincludes a centralized unitand a plurality of radio units-to-. The centralized unitcorresponds to the centralized unitshown in. The radio units-to-corresponds to the radio units-to-shown in. The radio units-to-transmits an upstream optical signal to the centralized unitby using the analog RoF. Since the radio units-to-have the same configuration, the radio unit-will be described as an example.

5 1 61 1 54 1 55 1 1 55 1 i n. The radio unit-includes a second electric/optic conversion unit-, an array antenna unit-, and antenna elements--to--

54 1 8 55 1 1 55 1 n. The array antenna unit-receives a radio signal transmitted from the wireless terminalvia the antenna elements--to--

61 1 55 1 1 55 1 n. The second electric/optic conversion unit-converts the radio signal received via the antenna elements--to--

4 48 49 i The centralized unitincludes a second optic/electric conversion unitand a signal processing unit.

48 7 The second optic/electric conversion unitconverts an optical signal received via the optical fiberinto an electric signal.

49 48 The signal processing unitgenerates upstream data by performing signal processing on the electric signal converted by the second optic/electric conversion unit.

3 i An operation example of the base stationwill be described below.

14 FIG. 3 i is a diagram showing an operation example of the base stationaccording to the eighth embodiment.

54 1 8 55 1 1 55 1 54 1 401 54 1 61 1 61 1 54 1 402 61 1 5 1 4 n i i. The array antenna unit-receives a radio signal transmitted from the wireless terminalvia the antenna elements--to--. The array antenna unit-converts the received radio signal into an electric signal (step S). The array antenna unit-outputs an electric signal corresponding to the upstream radio signal to the second electric/optic conversion unit-. The second electric/optic conversion unit-converts the electric signal output from the array antenna unit-into an optical signal (step S). At this time, the second electric/optic conversion unit-converts the radio signal into an optical signal by modulating the intensity of the optical signal with the radio signal. Thus, analog RoF transmission can be performed from the radio unit-to the centralized unit

61 1 7 1 403 7 1 4 48 7 404 48 49 i A second electric/optic conversion unit-transmits the converted optical signal via an optical fiber-(step S). The optical signal transmitted via the optical fiber-is received by a centralized unit. The second optic/electric conversion unitconverts the optical signal received via the optical fiberinto an electric signal (step S). The second optic/electric conversion unitoutputs the converted electrical signal to the signal processing unit.

49 48 405 49 The signal processing unitperforms signal processing on the electric signal output from the fourth optic/electric conversion unit(step S). As a result, the signal processing unitgenerates upstream data.

3 i By the base stationthat has the foregoing configuration, it is possible to obtain similar advantages to the advantages of the first embodiment on the upward direction.

5 In the second to seventh embodiments, as in the eighth embodiment, each radio unit may receive an upstream optical signal and transmit the signal to the centralized unit. In the case of this configuration, the centralized unit and the radio unitin each embodiment are configured as follows.

(Configuration of Upward Direction According to Second Embodiment)

4 5 1 5 4 5 1 5 b b b m i i i m The centralized unitand the radio units-to-in the second embodiment have the same configuration as the centralized unitand the radio units-to-in the eighth embodiment.

(Configuration of Upward Direction According to Third Embodiment)

5 1 5 61 1 1 61 1 52 1 1 52 1 51 1 61 1 1 61 1 4 45 48 1 48 43 1 43 49 42 7 44 1 44 48 1 48 c c m n n n c n c c n c n n The radio units-to-in the third embodiment includes a plurality of second electric/optic conversion unit--to second electric/optic conversion unit--instead of the first optic/electric conversion unit--to the first optic/electric conversion unit--, and a multiplexer instead of the demultiplexer-. Here, the multiplexer performs wavelength division multiplexing of the optical signal output from the second electric/optic conversion unit--to the second electric/optic conversion unit--. The centralized unitin a third embodiment includes a demultiplexer instead of the multiplexer, a plurality of second optic/electric conversion units-to-instead of the first electric/optic conversion units-to-, and a signal processing unitinstead of the signal processing unit. In this case, the demultiplexer demultiplexes the optical signal input through the optical fiber. The phase adjustment unit-to-adjusts the phase of the optical signal output from the demultiplexer. The second optic/electric conversion unit-to-converts the optical signal after the phase adjustment into n electric signals.

(Configuration of Upward Direction According to Modification Example of Third Embodiment)

5 1 5 61 1 1 61 1 52 1 1 52 1 51 1 61 1 1 61 1 d d m n n n. The radio units-to-in the modification example of the third embodiment includes a plurality of second electric/optic conversion unit--to second electric/optic conversion unit--, instead of the first optic/electric conversion unit--to the first optic/electric conversion unit--, and a multiplexer instead of the demultiplexer-. Here, the multiplexer performs wavelength division multiplexing of the optical signal output from second electric/optic conversion unit--to third optic/electric conversion unit--

4 45 46 48 1 48 43 49 42 7 44 1 44 44 1 44 48 1 d n d d n n The centralized unitin the modification example of the third embodiment includes a demultiplexer instead of the multiplexer, a multiplexer instead of the demultiplexer, the second optic/electric conversion units-to-instead of the first electric/optic conversion unit, and a signal processing unitinstead of the signal processing unit. In this case, the demultiplexer demultiplexes the optical signal input through the optical fiber. The phase adjustment units-to-adjust the phase of the optical signal output from the demultiplexer. The multiplexer multiplexes the optical signals whose phases are adjusted by the phase adjustment units-to-. The fourth optic/electric conversion unit-converts the multiplexed signal by the multiplexer to an electric signal.

(Configuration of Upward Direction According to Fourth Embodiment)

5 1 5 61 1 1 61 1 52 1 1 52 1 51 1 61 1 1 61 1 e e m n n n. The radio units-to-in the fourth embodiment includes a plurality of second electric/optic conversion unit--to second electric/optic conversion unit--instead of the first optic/electric conversion unit--to the first optic/electric conversion unit--, and a multiplexer instead of the demultiplexer-. In this case, the multiplexer wavelength-divides and multiplexes the optical signal output from the second electric/optic conversion unit--to the optical signal output from the second electric/optic conversion unit--

4 45 48 1 48 43 1 43 49 42 7 48 1 48 44 1 44 48 1 48 e n e e n e n n n. The centralized unitin the fourth embodiment includes a demultiplexer instead of the multiplexer, the second optic/electric conversion units-to-instead of the first optic/electric conversion units-to-, and a signal processing unitinstead of the signal processing unit. In this case, the demultiplexer demultiplexes the optical signal input through the optical fiber. The second optic/electric conversion units-to-converts the optical signal outputted from the demultiplexer into an electric signal. The phase adjustment units-to-adjust the phase of the electric signal output from the forth optic/electric conversion unit-to-

(Configuration of Upward Direction According to Fifth Embodiment)

5 1 5 61 1 1 61 1 52 1 1 52 1 51 1 56 1 55 1 1 55 1 61 1 61 56 1 61 1 1 61 1 4 48 43 49 42 f f m n n n n n f f d. The radio units-to-in the fifth embodiment includes a plurality of second electric/optic conversion unit--to second electric/optic conversion unit--instead of the first optic/electric conversion unit--to the first optic/electric conversion unit--, and a multiplexer instead of the demultiplexer-. In this case, the beam forming circuit-outputs a radio signal from an input port corresponding to an output port to which the antenna elements--to--which has received the radio signal are connected. The second electric/optic conversion units-to-convert the radio signal output from the input ports of the beam forming circuit-into an optical signal. The multiplexer wavelength-divides and multiplexes the optical signal output from the second electric/optic conversion unit--to the second electric/optic conversion unit--. The centralized unitin the fifth embodiment includes a second optic/electric conversion unitinstead of the first electric/optic conversion unit, and a signal processing unitinstead of the signal processing unit

(Configuration of Upward Direction According to Sixth Embodiment)

5 1 5 61 1 1 61 1 52 1 1 52 1 51 1 57 1 61 1 61 58 1 1 58 1 61 1 61 58 1 1 58 1 61 1 1 61 1 4 48 43 49 42 g g m n n n n n n n f f d. The radio units-to-in the sixth embodiment includes a plurality of second electric/optic conversion units--to second electric/optic conversion units--instead of the first optic/electric conversion unit--to the first optic/electric conversion unit--, and a multiplexer instead of the demultiplexer-. In this case, the antenna unit-outputs a radio signal to the second electric/optic conversion units-to-to which the feed--to--which has received the radio signal are connected. The second electric/optic conversion units-to-convert the radio optical signal output from the feeds--to--which have received the radio signal into an optical signal. The multiplexer wavelength-divides and multiplexes the optical signal output from the third optic/electric conversion unit--to the third optic/electric conversion unit--. The centralized unitin the sixth embodiment includes a second optic/electric conversion unitinstead of the first electric/optic conversion unit, and a signal processing unitinstead of the signal processing unit

(Configuration of Upward Direction According to Seventh Embodiment)

5 1 5 61 1 1 61 1 52 1 1 52 1 51 1 57 1 61 1 61 58 1 1 58 1 61 1 61 58 1 1 58 1 61 1 1 61 1 h h m n n h n n n n n. The radio units-to-in the seventh embodiment includes a plurality of second electric/optic conversion units--to second electric/optic conversion units--instead of the first optic/electric conversion unit--to the first optic/electric conversion unit--, and a multiplexer instead of the demultiplexer-. In this case, the antenna section-outputs a radio signal to the second electric/optic conversion units-to-to which the feeds--to--which has received the radio signal are connected. The second electric/optic conversion units-to-convert the radio signal output from the feeds--to--which have received the radio signal into an optical signal. The multiplexer wavelength-divides and multiplexes the optical signal output from the second electric/optic conversion unit--to the second electric/optic conversion unit--

4 48 43 49 42 f f d. The centralized unitin the seventh embodiment includes a second optic/electric conversion unitinstead of the first electric/optic conversion unit, and a signal processing unitinstead of the signal processing unit

(About Second Communication Mode)

5 8 5 8 5 1 5 8 5 5 1 5 2 5 1 5 2 8 8 8 8 5 1 5 2 i i m i i i i i The above explanation describes the configuration for the first communication mode between the radio unitand the wireless terminal-. Next, the configuration for the second communication mode between the radio unitand the wireless terminal-will be described. In the second communication mode, a plurality of radio units-to-and a single wireless terminal-communicates with each other. Here, as an example, the case where the radio unitis two units (radio unit-to-) will be described. The radio unit-to-in the second communication mode transmits a different signal to a single wireless terminal-. When the single wireless terminal-has a plurality of antennas, MIMO communication becomes possible. That is, when the single wireless terminal-has a plurality of antennas, the single wireless terminal-receives the radio signals transmitted from the respective radio units-to-and separates them by signal processing.

4 8 5 1 5 2 8 4 8 i i i The centralized unitor the wireless terminal-may use common signal processing methods (e.g., MIMO signal processing methods such as ZF (Zero Forcing), MMSE (Minimum Mean Squared Error), MLD (Maximum Likelihood Detection), etc.) to separate received signals. The radio unit-to-may transmit the same signal to a single wireless terminal-, and the centralized unitor the wireless terminal-may perform in-phase synthesis by using signal processing.

5 1 5 2 4 5 1 5 2 4 5 1 5 2 5 1 5 2 4 5 5 1 5 1 5 1 5 2 5 1 5 1 4 4 4 4 4 a c a c The radio units-to-in the second communication mode forms a beam according to the control of the centralized unit. The configuration of the radio units-to-and the centralized unitin the downward direction is any of the configurations of the first to seventh embodiments described above. The plurality of radio unite-to-may have the same configuration or different configurations. When the plurality of radio units-to-are configured differently, the centralized unithas a configuration corresponding to the configuration of each radio unit. For example, when the radio unit-is a configuration of the radio unit-in the first embodiment (radio unit-), and the radio unit-is a configuration of the radio unit-in the third embodiment (radio unit-), the centralized unitaggregates the configuration of the centralized unitin the first embodiment (centralized unit) and the configuration of the centralized unitin the third embodiment (centralized unit). It is to be noted that a plurality of overlapping structures may not be provided.

5 1 5 2 4 In the second communication mode, the configuration of the radio units-to-and the centralized unitin the upward direction is any one of the above-mentioned eighth embodiment and the configuration in the upward direction in the second to seventh embodiments.

(About Third Communication Mode)

5 8 5 8 5 8 8 8 1 8 2 4 5 5 1 5 5 4 5 1 5 4 5 1 5 5 1 5 4 5 i i i m m m m The above explanation describes the configuration for the first communication mode between the radio unitand the wireless terminal-. Next, the configuration for the third communication mode between the radio unitand the wireless terminal-will be described. In the third communication mode, a single radio unitand a plurality of wireless terminals-communicates with each other. Here, as an example, a case where a plurality of wireless terminalsare two wireless terminals (wireless terminals-to-) will be described. In the third communication mode, the centralized unitselects a communication target radio unitfrom among a plurality of radio units-to-. The communication target radio unitin the third communication mode forms a beam according to control of the centralized unit. The configuration of the radio units-to-and the centralized unitin the downward direction is any of the configurations of the first to seventh embodiments described above. The plurality of radio units-to-may have the same configuration or may have different configurations. When the plurality of radio units-to-are configured differently, the centralized unithas a configuration corresponding to the configuration of each radio unit. It is to be noted that a plurality of overlapping structures may not be provided.

4 The centralized unitmay use common signal processing methods (e.g., MIMO signal processing methods such as ZF, MMSE, MLD, etc.) to separate received signals.

5 1 5 4 m In the third communication mode, the configuration of the radio unit-to-and the centralized unitin the upward direction is any one of the above-mentioned configurations in the eighth embodiment and the configuration in the upward direction in the second to seventh embodiments.

(About Forth Communication Mode)

5 8 5 8 5 1 5 8 5 5 1 5 3 8 8 1 8 2 5 1 5 2 5 5 3 5 5 5 1 5 2 5 5 i i m i i The above explanation describes the configuration for the first communication mode between the radio unitand the wireless terminal-. Next, the configuration for the fourth communication mode between the radio unitand the wireless terminal-will be described. In the fourth communication mode, a plurality of radio units-to-and a plurality of wireless terminals-communicates with each other. The fourth communication mode is a combination of the second communication mode and the third communication mode. Here, as an example, the case where there are three radio units(radio units-to-) and two wireless terminals-(wireless terminals-to-) will be described. In this case, for example, the radio units-to-may operate as the radio unitin the second communication mode, and the radio unit-may operate as the radio unitin the third communication mode. When there are two radio units, one of the radio units-and-operates as the radio unitin the second communication mode and the radio unitin the third communication mode.

5 1 5 2 4 5 1 5 2 4 5 1 5 2 5 1 5 2 4 5 A radio unit-to-in the fourth communication mode forms a beam according to the control of the centralized unit. The configuration of the radio unit-to-and the centralized unitin the downward direction is any of the configurations of the first to seventh embodiments described above. The plurality of radio units-to-may have the same configuration or different configurations. When the plurality of radio units-to-are configured differently, the centralized unithas a configuration corresponding to the configuration of each radio unit.

5 1 5 2 4 In the fourth communication mode, the configuration of the radio unit-to-and the centralized unitin the upward direction is any one of the above-mentioned configurations of the eighth embodiment and the configuration of the upward direction in the second to seventh embodiments.

(Hardware Configuration Example)

15 FIG. 3 3 3 3 111 113 112 i i is a diagram showing a hardware configuration example of the base stationto(wireless communication device) in each embodiment. A part or all of each functional unit of the base stationtois realized as software by a processorsuch as CPU (Central Processing Unit) executing a program stored in memoryand memorywith a nonvolatile recording medium (non-transient recording medium). The program may be recorded on a computer-readable recording medium. The computer-readable recording media are non-transitory recording media, such as flexible disks, optical magnetic disks, ROM (Read Only Memory), CD-ROM (Compact Disc Read Only Memory) and other portable media, and hard disks and other storage devices built into computer systems.

3 3 i Some or all of the functional parts of base stationstomay be realized using hardware including electronic circuits (electronic circuit or circuitry) using for example, LSI (Large Scale Integrated circuit), ASIC (Application Specific Integrated Circuit), PLD (Programmable Logic Device) or FPGA (Field Programmable Gate Array) or the like.

Although the embodiments of the present invention have been described in detail with reference to the drawings, specific configurations are not limited to these embodiments, and designs and the like within a range that does not deviating from the gist of the present invention are also included.

The present invention is applicable to a wireless communication system.

1 Wireless communication system 2 Host device 3 3 3 3 3 3 3 3 3 3 a b c d e f g h i ,,,,,,,,,Base station 4 4 4 4 4 4 4 a b c d e f ,,,,,,Centralized unit 5 5 5 5 5 5 5 5 5 5 a b c d e f g h i ,,,,,,,,,Radio unit 7 Optical fiber 41 Radio unit selection unit 42 42 42 42 42 49 c d e f ,,,,,Signal processing unit 43 43 43 43 43 43 b c d e f ,,,,,First electric/optic conversion unit 44 Phase adjustment unit 45 Multiplexer 46 Demultiplexer 47 Wavelength control unit 48 Second optic/electric conversion unit 51 51 b ,Demultiplexer 52 52 b ,First optic/electric conversion unit 53 Array antenna control unit 54 Array antenna unit 55 Antenna element 56 Beam forming circuit 57 5 h ,Antenna unit 58 Feed 59 Reflect array 60 Transmit array 61 Second electric/optic conversion unit 111 Processor 112 Memory 113 Storage device 200 Radio unit